What is a battery?
A battery is an energy storage device and can be found in many different shapes, sizes, chemistries, voltages and capacities. Batteries are made up of individual cells, connected up to produce a given voltage and capacity.
Voltage and Capacity
The voltage of a battery is simply the nominal voltage of the basic cell technology multiplied by the number of cells in series. For example, an alkaline cell has a nominal voltage of 1.5v, and if 10 cells are connected in series, the resulting battery has a voltage of 15v.
The capacity of a battery is a function of the energy density of the chemistry, combined with the physical size of the cells used and the number of cells connected in parallel. For example, an alkaline D cell with a capacity of 20Ah can be connected in parallel with 4 similar cells to produce a capacity of 80Ah.
Combining multiple series and parallel strings is possible, but if larger capacity cells are available it is more commercially viable to use larger cells in the place of parallel connections if possible, as each parallel ‘string’ must have the same voltage. Therefore, to create a 15v 80Ah battery pack from alkaline D cells requires 40 cells – 4 parallel sets of 10 cells in series
Choosing the correct chemistry is critical to ensure that your project succeeds technically and commercially. Chemistry selection is highly project specific, and the implications of different choices must be thoroughly understood.
Each battery has a set of electrical characteristics that will help to determine suitability for a given project. These characteristics are mainly a function of the cell chemistry, but are also affected by the manufacturing processes and physical construction of the cells.
Rechargeable batteries should be chosen for products where there is adequate access to a power source for charging, and charge times fit well into the product usage profile. They offer greater convenience and electronic waste as they do not need to be replaced as often as non-rechargeable batteries. Typically, rechargeable batteries are found in handheld devices, consumer and industrial electronics, laptops, mobile phones and backup power systems.
Non-rechargeable batteries tend to be suited to applications where it is not cost effective to recharge the battery in situ. They can offer extremely long life and are frequently used in remote devices which are difficult to recover or require higher performance than a rechargeable battery can offer. Example applications include tsunami detectors, remote dataloggers for explosive atmospheres or downhole drill tools in oil and gas wells.